Velvetbean caterpillar (VBC) numbers are on the rise across south Georgia, and this is a good time to remind growers who may not have a professional crop consultant or scout that they need to check their fields for insect pests. Velvetbean caterpillar populations should be relatively easy to manage, but overlooking an infested field can lead to rapid defoliation. The point of this post is not to encourage growers to fire up the sprayer or add an insecticide to the next fungicide application. The point is that we need to be in the field scouting and making wise decisions based on current pest activity.
We scouted a field yesterday that was at threshold with a mixed population of velvetbean caterpillar (70%) and soybean looper (30%). Most of the larvae were small and there were a lot of VBC moths which tells me that feeding damage is likely to ramp up quickly in that field over the next 1o to 20 days if no treatment is applied. Not far away, we checked a different field that had virtually no caterpillar pressure or moth activity.
Folks who are not scouting on a regular basis should remember to check multiple locations (10 stops is a good number) within a field before making a management decision. Many times I have been called to look at a field that was “at threshold” for caterpillars only to find a hot spot in one area of the field and low numbers everywhere else. Our caterpillar thresholds are calculated in number of larvae per row foot. If you check three feet of row, the number of larvae counted should be divided by three. A standard beat sheet is three feet long; 12 caterpillars on the beat sheet is only 4 caterpillars per row foot and is not threshold for healthy, actively growing vines that have lapped the row middles.
UGA County Extension agents can help with choosing the most cost effective and efficacious insecticides when caterpillar populations reach economic thresholds. Our 2017 peanut crop has a lot of yield potential going into mid-August, and we can go along way toward preserving profit potential by monitoring pests and making timely management decisions.
For more information about foliage feeding caterpillars or other insect pests of peanut, contact your local UGA county Extension agent.